In sewer lines it is customary for manholes to be installed at various intervals such as where the sewer line changes elevation or direction. Conventional manholes are fabricated of cast concrete and are provided with one or more pipe-receiving ports which receive the ends of sewer pipes. In order to prevent ground water from infiltrating the manhole, and to prevent sewage in the manhole from leaking outwardly to pollute the ground water, seals or gaskets are normally used to seal the gap between the outer periphery of the pipe and the inner periphery of the port in the manhole.
Various types of seals have been proposed for this purpose. One such seal is disclosed in U.S. Pat. No. 3,759,280. This seal has a base fastened to, or embedded within, the concrete of the manhole around the pipe-receiving port and a neck which extends outwardly from the manhole along the outside of the pipe and which is fastened to the outer periphery of the pipe by a clamp.
Another pipe to manhole seal is disclosed in U.S. Pat. No. 3,813,107 and its companion U.S. Pat. No. 3,832,438. This seal has a generally triangular cross-section with a hollow pipe-engaging portion and a pair of outturned flanges which are molded into the concrete during pouring of the manhole.
Another pipe to manhole seal is disclosed in U.S. Pat. No. 3,874,063. This seal assembly has a portion molded into the concrete manhole and a lateral annular recess adapted to receive an annular wedge. The wedge is driven into the recess after the pipe has been installed to provide a fluid-tight connection.
U.S. Pat. Nos. 4,159,829, and its companion 4,073,048, each disclose another type of gasket for a sewer pipe to manhole connection. This patented gasket has a hollow pipe-engaging portion and a T-shaped base which is molded into the concrete while the manhole is being poured.
U.S. Pat. No. 4,103,901 discloses a pipe to manhole seal having a base portion molded into the concrete of the manhole and a pipe-engaging portion adapted to be secured around the pipe by a pipe clamp.
U.S. Pat. No. 2,257,119 discloses several different embodiments of a seal for a cylindrical member such as a shaft.
While each of the above disclosed patented devices may function satisfactorily for its intended purpose, none has all of the attributes of a commercially desirable seal. For instance, such a seal should provide leak resistance up to 10 psi. and should enable the pipe to be deflected omnidirectionally up to 20.degree. with respect to its receiving port. A satisfactory pipe seal should also prevent the pipe from contacting the bottom of the pipe-receiving port in response to transverse shear loads on the pipe as may be imposed by backfill and traffic loads adjacent the manhole. The seal should also be sufficiently compressible as to accommodate variations in the outside diameters of pipes of different materials which have the same nominal inside diameters. The seal should also be mounted securely in place and should be capable of in-field adjustments and repair to accommodate unusual situations. A desirable seal must also be sufficiently foolproof as to be capable of being installed by relatively unskilled labor, and the seal must be capable of being installed rapidly and in a minimum amount of time.